There seems to be very little information on a 4000mah li-ion battery swap for the vita with the exception of 2 Youtube videos that really don't go into much detail, particularly for users with the 3G model Vita. So I am here to somewhat show you all how I was able to throw in a massive 4000mah li-ion battery into my 3G Vita (PCH-1101). Before I start however I want to get the obvious out of the way....

1) You do this mod at your own risk.
2) for those with 3G model Vita, this mod will PERMANENTLY disable 3G (not like it matters anyways as the service is no longer available)
3) This mod WORKS. You should expect about 2x playtime and around 1-1.5hour extra charge time. I got about 7hours playtime in Killzone: Mercenary with screen at around 65% brightness.
4) You will need soldering iron, solder, 606090 li-ion battery, pliers, electrical tape and a dremel(primarily for 3G vita owners, wi-fi owners really dont need this)

Here is the battery model # I used : 606090 3.7v 4000mah

1) Now, once you get your Vita opened up, remove the old battery and take out its voltage control pcb (the board is hidden inside the gray plastic top were wires come out. Simply peel back outer silver sticky housing of battery to remove gray top). Solder Red wire to "+" on li-ion and black wire to "-".

2) Go ahead and also remove the voltage control pcb on your li-ion battery by unwrapping the yellow translucent tape. Cut off PCB. Note that you will have a difficult time soldering to the positive lead off the li-ion so make sure you cut past the pinch weld (basically cut this lead as close to the PCB as you can). Then solder the red wire to the positive lead (marked on battery) and black wire to the negative lead. Solder to PCB from STOCK battery that you removed earlier. "B+" is positive (red wire), "B-" is negative (black wire). I personally epoxy-d the battery pcb to the back plastic. Do not epoxy the battery itself.

3)FOR 3G VITA OWNERS ONLY!!! You will need to remove the 3G card, all 3 of its wires, as well as the SIM card reader off to the right hand side(as none of the components are useful anymore). Now, take dremel and grind away the RIGHT hand side silver post that the 3G card was scr..ed in to. I accidentally nicked my motherboard in this area(pictured), but it is okay as that area is just grounding for the 3G card anyways. Also, you MUST remove the white/beige connector that the 3G card was plugged into. If you do not do this, your vita will not close up! Cover up the area were you removed the 3G connector with electrical tape as some of those tiny pads on mobo will still be live. I also covered up my boo-boo from the dremel with electrical tape.

4)Here's my vita mobo with electrical tape in spots I messed with. Your vita needs to looks identical to this. There should be no other PCB attatched to vita or any other plastics. Only thing that should be left from the 3G set-up is the LEFT hand post.

5)When you hook up everything and have verified that the battery is plugged in as well as the rear touch pad, do not be alarmed if your vita does not turn on from the power button. Plug in vita to wall charger. ALLOW BATTERY TO FULLY CHARGE. Could take a few hours. It took mine about 2.5hours. This is needed ONLY for the very first boot after installing new battery. After this initial set-up you can turn on your vita using power button on top as normal.

6)When you do boot it up, date and time will have been reset. All of your other data is still there, no worries.

7)3G OWNERS ONLY. Upon boot up you will receive this message basically stating that there is a problem with a mobile network feature ( this is referring to 3G). Simply hit "ok". Message will reappear on every reboot. Your vita is now wi-fi only and now has a much longer battery life!

Congrats! Your 3G vita is now a wi-fi only Vita but you now have a wopping 4000mah monster powering it! I have not messed with a 2000-series vita yet, so please don't ask if this mod works in it because I don't have that vita. This method works for ONLY the PCH 1xxx series with our beautiful OLED display

In the near future, I am planning on doing a USB Type-C port mod to replace the Accessory port (port next to game card port) as well as a Micro Sd-card reader to replace the SIM card reader. Stay tuned.

Thanks for the guide! The images were broken in line but I was able to see them in a new tab.
I use a PSVSD for mine but the extra battery life sounds delicious! I'm looking forward to your Type-C mod.